This invention relates to an indicator mechanism in a pushbutton tuner, and more particularly to improvements in a mechanism to mount a slidable plate for moving a pointer arm supporting an indicating pointer on a front plate formed on a casing of the tuner.
A well-known indicator structure, as shown in FIG. 1, generally comprises a pointer arm 2 provided with an indicating pointer 1 at the top end thereof. A slidable plate 4 is pivotally connected to the pointer arm 2 by a pin 3 in one hand and on the other hand, it is pivotally mounted on a front plate 5 formed on the casing by means of a pivot 6. In the lower surface of the slidable plate 4 is supported an end of a pin 7. The other end of the pin 7 is inserted in a long slit 9 formed in a slidable bar 8 which is arranged to interlock with a pushbutton (not shown) of the tuner. When the pushbutton is pushed to cause movement of the slidable bar 8, the slidable plate 4 engaged with the slidable bar 8 through the long slit 9 and the pin 7 is rotated thus to move the pointer arm 2 to a predetermined position. As illustrated the pointer arm 2 is formed with a protrusion 10 at the base end thereof and the protrusion 10 is disposed in a guide slit 11 formed in a rear wall of the casing, thus allowing the pointer arm 2 to pivot on its base end.
The reference numeral 2' designates a torsion spring provided around the pin 3 in order to avoid deviation of the indicating pointer 1, which may be caused by looseness at the junction between the pointer arm 2 and the slidable plate 4.
FIG. 2 and FIG. 3 show more clearly how the slidable plate 4 is pivotally mounted on the front plate 5 of the casing.
In FIG. 2, the front plate 5 and the slidable plate 4 are shown put together so that their through bores 5' and 4' are aligned with and adjacent each other. A plate spring 12 is then laid over the slidable plate 4 and a plastic rivet 13 secures these three elements together.
Since the rivet 13 is made of a plastic material, a loose connection of the elements is possible, which is reduced by the plate spring 12. However, the plate spring 12 is not effective enough to prevent the junction from loosening when a sudden force is applied to the slidable plate. For example, looseness at the junction between these elements is caused by impacts generated by acceleration applied to the pointer arm and the slidable plate when the pushbutton is pushed, thus causing deflection of the indicating pointer 1.
As shown in the modified prior art embodiment of FIG. 3, a pin 14 is fixed on the front plate 5. The pin 14 is inserted in the through bore 4' of the slidable plate 4, and thereafter, the front plate 5 and the slidable plate 4 are fixed together by means of an E-ring 15 provided on the pin 14. However, such a construction is expensive.